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NEW YORK STATE MUSEUM 



interior the delthyrium is relatively broad and has encroached upon 

 the beak, the pedicle cavity is deep, the teeth stout and thick. The 

 adductor scars are very long, flabellate and extend almost to the 

 anterior margin. They are bounded at the sides by the thickened 

 extension from the teeth but in front they are not deeply impressed. 

 They are divided by a median septum which almost reaches the 

 margin. The diductor scar is elongate oval and posterior. 



The dorsal valve is more regularly convex though flattened 

 medially with angular slope in all directions. It is sinused on- 

 the anterior margin. The beak is blunt and the margins slope away 

 from it at a low angle. On the interior the socket walls are stout 



Rhipidomella lehuquetiana 



and high, the sockets moderately deep and the cardinal process 

 rather feebly developed, being fused with the adjoining walls and 

 not projected beyond the hinge line; it is not divided. The mus- 

 cular scars are posterior in a single or double subcircular pair- 

 separated longitudinally by a broad low and short ridge. 



Dimensions. These shells measure in full growth about 15 mm 

 in width by 12 mm in length. 



This peculiar little shell which is quite abundant, bears the char- 

 acters of senility as expressed in its thickened shell and shell pro- 

 cesses and the usual resorption of the beak by the delthyrium. It 

 has the general characters of Rhipidomella modified to the expres- 

 sion presented by O r t h i s d u b i a of the St Louis limestone 

 [see Pal. N. Y. v. 8, pt i, pi. 6A, fig. 18-22] which is a gerontic 

 form with such outline. 



Lozver Devonic. Lehuquet's beach, Grande Greve, P. O. 



Rhipidomella hybridoides nov. 



But for the extravagant size this shell attains at full growth it 

 would be quite impracticable to distinguish it from American forms- 



